A phone number is private. Although people may selectively share their personal phone numbers with others to maintain an interpersonal communication, they do not want to spread their personal phone numbers easily so as to prevent fraudulant calls, various advertisements and spam short messages.
In the conventional techniques, when one party needs to call another party, the calling party generally needs to know the phone number of the called party. For example, when making a delivery, a courier needs to get in touch with a recipient; normally, the courier may call the recipient according to the phone number recorded on the express waybill. Thus, a logistics company is able to accumulate names and phone numbers of many recipients over time. However, in some cases, once those accumulated names and phone numbers are disclosed accidentally or revealed maliciously to a third party, there may be trouble for the users of those phone numbers, such as the aforementioned fraudulant calls, advertisements and spam short messages.